Unsteady hot fire atomization measurements in injector sprays

Acoustic oscillations were induced in a sub-scale liquid rocket engine that burned liquid oxygen and gaseous hydrogen as propellants. The oscillations in the chamber were forced by a rotating gear just downstream of the nozzle throat. High frequency data was acquired for pressure and velocity via a pressure transducer and a magnetic flowmeter. A cross correlation was performed on the velocity and pressure signals to determine the amplitude and phase difference of the two signals. An linearized onedimensional acoustic model was developed to simulate the mean and unsteady flow within the chamber with mass and energy addition. The phase difference between unsteady pressure and velocity was determined from the model and fit to match the phase difference measured by the experiments. The points where the modeled and experimental phase differences agreed determined the real part of the propellant evaporation and combustion pressure- and velocity-coupled response functions.